Television receiver



July 8, 1941. DESERNQ 2,248,815

TELEVISION RECEIVER Filed July 22, 1939 [n yen for 6 fer Peder/70 by ZPatented July 8, 1941 2,248,815 I TELEVISION RECEIVER Peter Deserno,Berlin, Germany, assignor to C. Lorenz Aktiengesellschaft,-Berlin-Tempelhof, Lorenzweg, Germany, a company Application July 22,1939, Serial No. 285,836 In Germany August 4, 1938 6 Claims.(0,1.250-27) This invention relates to television receivers, and moreparticularly to new and useful means for eliminating certain troublesheretofore observed in such devices.

It is a fact known to everyone skilled in theart that individualinstrumentalities, such as the image amplifier, the time base circuitsand the like, forming part of a television receiver fed from the mainssupply, demand a certain building-up time from the moment at whichthereceiver is switched in circuit with such current source to themoment at which the receiver is ready to operate. This delay inoperation thus introduced by the above mentioned building-up time isdisadvantageous in several respects. For instance, in cases that thefull anode voltage" is applied across the cathode ray tube during suchbuilt-up time, the life of this tube will be considerably reduced.Furthermore the fluorescent screen of the cathode ray or Braun tube willbe subject to damage if the cathode ray prior to the operation of thetime base circuits continually remains on the same spot of thefluorescent screen. Moreover, the appearance of an indefinite image onthe fluorescent screen before the receiver has actually acquired perfectsynchronism is very annoying. All these troubles in coaction with oneanother will undoubtedly give the observer the impression that thereceiver is out of order. These difliculties are also noticed when theoperator disconnects the receiver from the mains supply.

According to one object of this invention, the above mentioneddifficulties are eliminated by the provision of means which during apredetermined period of time immediately after the receiver has beenconnected to the power circuit prevents that a cathode ray becomesproduced by the cathode ray tube, and which upon opening this circuitwill immediately extinguish the cathode ray.

It is a further object of my invention to prevent the formation of thecathode ray by decreasing the normal potential of the auxiliary anode orof the focusing lens of the cathode ray tube. The delay for this periodof time is determined by thermostatic means, while the cathode ray isextinguished by a contact which is mechanically coupled with the powerswitch of the receiver.

My invention will be more readily understood from the followingdescription taken in conjunction with the accompanying drawing, thesingle figure schematically illustrates one embodiment according to thisinvention.

' in this drawing, reference letter B indicates the throat portion ofthe cathode ray tube illustrative for this invention, the remainingparts of which have been omitted for the sake of simplicity sinceimmaterial for the scope of this invention. Reference letter K denotesthe cathode, S the auxiliary anode, L the focusing electrode and A theanode of this tube. ous electrodes normally receive their proper'con-The varitrol potentials from a potentiometer device connected across anysuitable potential source Q;

the negative pole of this source is connected to the cathode K and alsoto ground.

For carrying out the indicated operation of this device, a particularoperating circuit is branched off from the power supply with theobject'to operate a thermostatic relay T, which inturn controls acontact t with a predetermined time delay. This contact is disposedbetween the ground pole of the source Q and either of the electrodes Lor S of the cathode ray tube B. A switch A mechanically coupled with themain switch C of the receiver D is interposed in series with theoperating circuit. A further contact 1', mechanically coupled with theswitch A,

is interposed in a path shunted across the contact t.

It will now be assumed that the receiver has just been switched in,which condition is shown in the drawing. Since either of the electrodesS or L is directly connected to ground over the closed contact t, thetube B is unable to produce a cathode ray. The switch A is closed sothat the thermostatic relay T is energized from the mains supply. Afterthe elapse of a predetermined period of time which corresponds to thebuilding-up time of the various circuits of the receiver, this relayoperates to open the contact if. Because of the fact that the contact 1'was opened when the switch A was closed, ground is removed from theelectrode S or L which now acquires its proper control voltage from thepoteniometer with the result that the cathode ray is immediatelyproduced.

Upon disconnecting the receiver, the switch A is opened and the contactr in turn closed, thereby bringing the electrode mentioned above to theearths potential thus immediately extinguishing the cathode ray. Inresponse to this disconnection, the thermostatic relay T is allowed tocool and to restore its contact t to normal in order to maintain theelectrode S or L at ground potential when contact r again becomes openedwhen the receiver is again switched in.

In order to immediately extinguish the cathode ray also in cases whenthe plug connector is involuntarily removed or when line faults occur, aspecial relay G may be provided which is normally operated from themains supply and which in a de-energized condition connects either ofthe electrodes S or L directly to ground.

What is claimed is:

1. In a television receiver, means for closing and opening a feedcircuit between the said receiver and a mains supply for rendering saidreceiver eifective and inefiective, a cathode ray tube normally adaptedto produce a cathode ray during the effectiveness of the said receiver,relay means for grounding one of the electrodes of said tube responsiveto the closing of the said circuit for preventing during a predeterminedperiod of time the said cathode ray tube from producing a cathode ray,and. means responsive to the opening of the said circuit for groundingsaid one of said electrodes for immediately extinguishing the cathoderay which is produced by the said cathode ray tube after the lapse ofthe said period of time.

2. In a television receiver, means for closing and opening a feedcircuit between the said receiver and a mains supply for rendering thesaid receiver effective and inefiective, a cathode ray tube comprisingat least a cathode and an auxiliary anode, a potential source normallymaintaining the said auxiliary anode at a proper control potential forcausing the said cathode ray tube to produce a cathode ray during theefiectiveness of the said receiver, means responsive to the closing ofthe said circuit for changing the potential of the said auxiliary anodein order to prevent during a predetermined period of time that thecathode ray tube forms a cathode ray, and means responsive to theopening of the said circuit for grounding said auxiliary anode andimmediately extinguishing the cathode ray which is produced by the saidcathode ray tube after the elapse of the said period of time.

3. The invention according to claim 2, characterized in that the saidmeans responsive to the closing of the said circuit is a slow operatingthermostatic relay having its back contact interposed between the saidcathode and the said auxiliary anode for interrupting this path after apredetermined period of time.

4. The invention according to claim 2, characterized in that the saidmeans responsive to the opening of the said circuit is a contactinterposed in a path between the said cathode and the said anode forclosing this path when the said circuit is opened and said means lastmentioned is mechanically interconnected with a switch means whichserves to open said circuit.

5. The invention according to claim 2, characterized in that the saidmeans responsive to the opening of said circuit is a contact interposedin a path between the said cathode and the said anode and that a furtherrelay normally operated from the mains supply is used in order toimmediately extinguish the said cathode ray when line fault-s occur.

6. In a television receiver means for closing and opening a feed circuitbetween said receiver, a mains supply for rendering said receivereffective and ineffective, a cathode ray tube normally adapted toproduce a cathode ray during the efiectiveness of the said receiver, aswitch for controlling said mains supply and contact means mechanicallyconnected to said switch for grounding a control electrode of said tubeand immediately extinguishing said cathode ray, responsive to theopening of said switch.

PETER DESERNO.

